When it comes to acceleration and speed dont forget to factor in the power to weight. Mark brings up a good point about the riders weight having to do with the faster speeds on the ski. Just imagine the kid on a spark with a tune or even the impeller mod, he will fly regardless.Everyone talks like it's just the tune. There's a lot of other stuff on there and the kid is half he weight of the average male adult. In spite of all of that it's only a few mph faster than a stock 90 with a 220 pounder on the seat.